Hello Felipe! and welcome to the community!
Reading your problem, I directly guess that the board is not booting properly, maybe because some boot pin it’s being connected to any GND or Vcc. But, to make sure, please say what is the exactly board that you are using and specify the circuitry of your project if you have created anyone.
However, if you add “#include DEBUG” in the first line of the example code and make an instance of serial port on de setup(), you will be able to see all transmission and authentication data into the serial port inspector. If there is any problem you could see it there.
If it only writes an un comprehensible line of characters, you have any problem in the board or in the booting wire up.